Thin-film display panels (such as LCD or electroluminescent) have been known to be very useful for displaying information inasmuch as the thin-film structure, including the cross electrodes, can be deposited on a glass substrate thereby providing a matrix display panel capable of being selectively energized to activate individual pixels thereon. One of the problems encountered in the manufacturing of thin-film display panels is the development of processes that pattern the thin-film electrode structures.
Most thin-film devices have had their thin-film electrode structures patterned either by a wet process known as photolithography or by shadow masking. Photolithography is very similar to processes used to develop photographs in that the deposit to be patterned is coated with light-sensitive material, which is then exposed to a negative or a positive pattern and then developed and later stripped in various corrosive developing solutions. The disadvantages of this method is that it is slow and labor intensive, and involves many steps, each one subject to failure or possible contamination of the thin-film device.
With respect to the use of shadow masking to deposit thin-film structures, reference is made to U.S. Pat. No. 4,335,161 to Fang C. Luo, entitled "THIN-FILM TRANSISTORS, THIN-FILM TRANSISTOR ARRAYS AND A PROCESS FOR PREPARING THE SAME". In summary, the Luo patent appears to disclose a method of preparing a thin-film transistor or an array of thin-film transistors by depositing in vacuum the different components through a single apertured mask wherein the apertured mask is moved in a predetermined pattern for the deposition of each of the components. In the process, semiconductor material is deposited through the mask and then the mask is moved in a direction a distance equivalent to the longest dimension of the openings in the mask. Throughout the thin-film transistor formation process the mask is moved several times in different directions. The assembly that is then formed is removed from the vacuum and the fabrication completed by techniques such as photolithography.
As in Luo, shadow masking is usually performed over small substrates with stiff masks that are manually clamped to ensure even contact with a particular substrate. This is a relatively slow process and usually requires breaking vacuum in the deposition chamber, resulting in some thin-film contamination. When depositing through a large area mask, it is common that the substrate is not perfectly flat or not level with respect to its surrounding substrate holder. The present invention addresses this and other problems arising from the difficulties of remote automatic handling of large area shadow masks in in-line deposition systems.
A method which would produce thin-film structures without the use of photolithography would be considered a significant advancement in the thin-film structure deposition art. In addition, it is also believed that a mechanism which would support the shadow mask while relieving stress in the mask during deposition would constitute a significant advancement in the art.